In the manufacture of a semiconductor device, micro processing by lithography using a photoresist has been performed. The micro processing is a processing method including forming a thin film of a photoresist on a semiconductor substrate such as silicon wafer, irradiating actinic rays such as ultra violet rays through a mask pattern on which a pattern for a semiconductor device is depicted to develop, and etching the substrate by using an obtained photoresist pattern as a protective film, thereby forming fine unevenness corresponding to the pattern on the surface of the substrate. However, in recent progress in high integration of semiconductor devices, shorter wavelength actinic rays tend to be used. For example, an ArF excimer laser (193 nm) has been taking place of a KrF excimer laser (248 nm). Along with this change, influence of reflection of actinic rays from a semiconductor substrate has become a serious problem. Accordingly, a method to provide an antireflective film (bottom anti-reflective coating) between the photoresist and the substrate has been widely studied to resolve the problem. For the anti-reflective coating, many studies have been made on an organic antireflective film made of a polymer having light absorption groups or the like due to the easiness of use or the like. For example, an acrylic resin type antireflective film having hydroxyl groups as cross-linking reaction groups and light absorption groups in the same molecule, a novolac resin type antireflective film having hydroxyl groups as cross-linking reaction groups and light absorption groups in the same molecule and the like are included.
As properties required for an antireflective film, the film has large absorption to light and radiation rays; the film causes no intermixing with a photoresist (insoluble in a photoresist solvent); the film does not cause diffusion of low molecular weight substances from the antireflective film to the upper layer of a photoresist during heating and baking; the film has a higher dry etching rate than that of a photoresist; and the like.
In recent years, in order to solve wiring delay which has become clear in accordance with miniaturization in a pattern rule of semiconductor devices, it has been considered to use copper as a wiring material. With the consideration, applying a dual damascene process as a wiring forming method on a semiconductor substrate has also been considered. In a dual damascene process, an antireflective film is formed on a substrate in which via holes are formed and which has a high aspect ratio. Therefore, the antireflective film used in this process is required to have filling property by which holes can be filled without gap, flattening property by which a flat coating is formed on the surface of a substrate, and the like.
However, it is difficult to apply materials for an organic-based antireflective film on a substrate having a high aspect ratio, and in recent years, materials with a particular emphasis on filling property or flattening property have been developed (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).
In addition, in recent years, a film known as a hard mask containing metal elements such as silicon and titanium has been used as an underlayer film disposed between a semiconductor substrate and a photoresist (see, for example, Patent Document 4, Patent Document 5, Patent Document 6 and Patent Document 7). In this case, since a photoresist and a hard mask have large difference in their constituent components, their removing rates by dry etching significantly depend on a type of gas used in the dry etching. The hard mask can be removed by dry etching without significant decrease of the film thickness of the photoresist by selecting an adequate type of gas. Therefore, it is considered that when the photoresist and the hard mask are used, sufficient film thickness as a protective film (which is formed with the photoresist and the hard mask) for semiconductor substrate processing can be ensured, even if the photoresist is a thin film.
Various polymers are used as a resist underlayer film in a lithography process (see, for example, Patent Document 8, Patent Document 9, Patent Document 10, and Patent Document 11).
[Patent Document 1]
Japanese Patent Application Publication No. JP-A-2002-47430
[Patent Document 2]
WO 02/05035 pamphlet
[Patent Document 3]
Japanese Patent Application Publication No. JP-A-2002-128847
[Patent Document 4]
Japanese Patent Application Publication No. JP-A-11-258813
[Patent Document 5]
Japanese Patent Application Publication No. JP-A-2001-53068
[Patent Document 6]
Japanese Patent Application Publication No. JP-A-2005-55893
[Patent Document 7]
Japanese Patent Application Publication No. JP-A-2005-15779
[Patent Document 8]
WO 03/017002 pamphlet
[Patent Document 9]
WO 04/034148 pamphlet
[Patent Document 10]
WO 05/098542 pamphlet
[Patent Document 11]
WO 06/115074 pamphlet